1. Field of the Invention
The present invention relates in general to disk storage systems and more particularly, to methods and apparatus for distinguishing the effects of adjacent track encroachment from head thermal movement.
2. Description of the Related Art
Disk drives are magnetic recording devices used for the storage of information. The information is typically recorded on concentric tracks on either surface of one or more magnetic recording disks. The disks are rotatably mounted to a spin motor and information is accessed by means of read/write heads that are mounted to actuator arms which are rotated by a voice coil motor. The voice coil motor is excited with a current to rotate the actuator and move the heads. The read/write heads must be accurately aligned with the storage tracks on the disk to ensure proper reading and writing of information. The read/write heads read recorded information from the surface of the disk by sensing the magnetic transitions emanating from the surface of the disk. To write on a data track, current is applied to the read head. The current generates a magnetic field, which magnetizes the surface of the disk.
Recording density may be increased by reducing the width of recording tracks. However, as recording tracks become narrower in physical dimensions, the amount of write current applied to the head may result in erasing data located on adjacent tracks. This is of concern when the write current that is applied is too high. Such a characteristic of the head is known as adjacent track encroachment (ATE). The increase in temperature resulting from the write current may also cause the slider on which the head is mounted to move off the centerline of the track. When the slider cools down, the head may move in the opposite direction. Such movement may be as much as 5 micro-inches for certain heads. Such an effect is typically referred to as head thermal movement. The effects of head thermal movement is typically similar to that of ATE. As a result, it is difficult to distinguish between the effects of ATE and head thermal movement. However, ATE results from an intrinsic property of the head, while head thermal movement is a system characteristic. It desirable to be able to distinguish the effects of these two factors, so as to be able to determine the quality of a head and system performance.
The present invention is a method and system to determine a quality of a head in a hard disk drive. The method comprises providing a disk having a at least one side with a plurality of tracks, writing on a predetermined track on the plurality of tracks and reading a profile of the predetermined track to provide a first profile value. The head is then moved to an adjacent track where it writes on the adjacent track. A profile of the predetermined track is then read to provide a second profile value. A quality of the head can then be determined based on the first and second values.